Diesel Engine Longevity Revisited

Clark September 12th, 2019

Some years ago I wrote this blog post about the longevity we can expect from marine diesels. I pointed out that the engines on our family ferries often went over 20,000 hours – once to 26,000 – before a rebuild. Those were the old Ford engines, which were replaced with John Deere engines about eight years ago.

We have finally had to swap out the first John Deere for a rebuild…after 46,000 hours, the equivalent of running it 24 hours per day for over five years straight.

Now these engines have a markedly different usage pattern than most marine diesels. That is, they are hammered hard, sometimes for 24 hours a day, making 400-yard trips, with the operator slamming them back and forth between forward and reverse dozens of times per hour, which leads to the first lesson: They like this. Diesel engines like to be hammered. It makes them happy.

The second lesson is that people who talk about rebuilding diesels after 3000-5000 hours are doing something wrong, which in most cases is under-using, and under-abusing the engine.

The only new practice I’ve added to my diesel maintenance repertoire is to send out an occasional oil sample for analysis. Blackstone Labs in Fort Wayne, Indiana did a good job of this, and will even mail you a free test kit and instructions. The analysis tells you a lot about what’s wearing in your engine, about how well your oil is holding up, and about any changes you should make in your engine oil or oil change interval. In my case they said I could change my oil every 120 hours, while I’ve been shooting for every 100, so that saves me money!

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Comment by Richard Cassano
2019-09-13 13:21:42

Well, I agree with you on running them hard, however, when doing an ocean trip with little wind, motoring is the way to go unless you don’t mind sitting and waiting for wind. In the interest of managing fuel I keep my 55 Hp diesel at 2100 RPM’s which is not considered hammering it hard. With that in mind, what should a total rebuild cost? I believe rebuilding is more economical then re-powering provided parts are available for a 33 year old Yanmar.

Comment by Clark
2019-09-13 14:01:19

Pretty rare to find an engine that you can’t get a rebuild kit for, definitely no problem for a Yanmar. If you pay somebody else to rebuild your engine it’s going to involve some yard bills/crane bills, then that person’s time, and the parts. The parts are shockingly cheap…less than $1000 for almost any diesel. Having never done it, I can’t say all that’s involved, but to press cylinder liners out, and back in, to an engine block is going to take a big hydraulic press. You’ll need dial indicators, calipers, straight edges – very precise and specialized measuring instruments that’ll set you back hundreds, but I don’t think the process it prohibitively difficult for a DIYer with solid shop skills, the time, and the inclination. I’m ready to rebuild my Perkins someday, but it just…keeps…going.

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